1. Eye

2. Human head

3. Objectives
How the structural components of the eye contribute to the overall function of observing the visual world

4. Objectives
Identify strategies (mechanisms) employed in the eye to provide nutrients and structural support without distorting light

5. Outline Overview Cellular structures through which light passes
Cornea
Lens
Retina
Structures which influence the image
Iris
Ciliary bodies
Trabecular meshwork

17. Eye

18. Turn the eye so that it is facing you & examine these structures on the front surface of the eye:
eyelids - two moveable covers that protect the eye from dust, bright light, and impact
sclera - this is the tough, white outer coat of the eye that extends completely around the back & sides of the eye
cornea - a clear covering over the front of the eye that allows light to come into the eye (preservative often makes this appear cloudy)
iris - round black tissue through the cornea that controls the amount of light that enters the inner part of the eye (may be colored in humans)
pupil - the round opening in the center of the eye that allows light to enter and whose size is controlled by the iris

19. V. Glossary of terms on the eye
Anterior chamber -space between cornea and iris or lens - contains aqueous humor
Aqueous humor -clear fluid, pressure regulated
Bowman's membrane -acellular, glycosaminoglycans, rich layer of cornea
Canal of Schlemm -carries fluid from trabecular meshwork to bloodstream
Choroid -vascular layer
Choroid plexus -vascular plexus, supplies nutrients to retina
Ciliary body -attach zonules from lens, contraction of ciliary muscle alters shape of lens
Ciliary epithelium -secretes aqueous humor
Ciliary process -pigmented and non-pigmented epithelium
Conjunctiva -stratified squamous or columnar, covers white of eye and inside eyelid
Cornea -structural layer, course focus of image on retina

20. Corneal endothelium -water transport cells Corneal epithelium -stratified squamous, protection Corneal stroma -fibroblasts and collagen, avascular Descemet's membrane -basement membrane of endothelium of cornea Fovea -bull's eye of macula Glaucoma -serious eye disease, obstruction of outflow of aqueous humor which raises intraocular pressure Iris -regulate amount of light entering eye Iris muscles dilator -open pupil, myoepithelium constrictor -close pupil, smooth muscle Lens -focus image on photoreceptor cells, avascular Lens epithelial cells -cells on anterior surface, source of lens fibers Limbus -sclerocorneal junction

21. Macula -cones, most sensitive, devoid of blood vessels, ganglion cell and internuclear layer Optic -nerve cap or head- blind spot, no photoreceptor cells Optic nerve -connect brain with eye Photoreceptor -photosensitive cells rods -black and white, rhodopsin pigment cones -red, green, blue pigments Pigmented epithelium of iris -block out light Posterior chamber -space between lens and iris - contains aqueous humor Retina -photosensitive part of eye pigmented epithelium -absorbs light outer nuclear layer -nuclei of photoreceptor cells internuclear layer -nuclei of bipolar neurons ganglion cell layer -transmit to brain through optic nerve Retinal pigmented epithelium -phagocytotic, prevents backscatter, melanin, Vitamin A storage

22. Root of iris -attachment of iris to sclera
Sclera -structural layer, white of eye, connective tissue
Scleral spur -enlargement of sclera, site of anterior attachment of ciliary muscle
Trabecular meshwork -resistance to aqueous humor outflow baffle of endothelial cells draped over connective tissue
Transparent retina -all retina except retinal pigmented epithelium
Uvea vascular layer of eye = iris, ciliary body, ciliary processes, and choroid
Vitreous body -fine filaments, jellylike, pressure on retina
Zonules -ligaments of lens that attach lens to choroid and ciliary

24. Eye

26. Three Layers of the Wall of the Eye
1. Supporting, 2. Vascular, and 3. Retinal layers
Uvea

27. Retina

29. Eye 192 human and 34412 monkey Aqueous humor 192 34412
Connective tissue
Aqueous humor
Nerve
Posterior chamber
192
Retina
Cornea
Sclera
Pupil
Optic nerve
Anterior chamber
What is the function of the canal of Schlemm
The canal of Schlemm functions to drain the aqueous humor from the anterior chamber.
Where is aqueous humor produced?
Aqueous humor is produced by ciliary processes. It then flows into the posterior chamber of the anterior cavity, through the pupil into the anterior chamber, and finally drains through the canal of Schlemm.
What is the ora serrata?
The ora serrata is the serrated junction between the retina and the ciliary body.
What are the functions of the pigment epithelial layer of the retina?
Absorbs scattered light that passes through the neural layer
Part of the protective blood-retina barrier isolating retina photoreceptors from the highly vascular choroid and regulating ion transport between these compartments.
Role in retinal regeneration
Phagocytosis of shed components from the adjacent photoreceptors and degradation of this material
Removal of free radicals by various protective antioxidant activities and support of the neural retina by secretion of ATP, various polypeptide growth factors, and immunomodulatory factors
The sphincter pupillae muscle is innervated by what portion of the nervous system?
Parasympathetic innervation
What are fovea centralis and the macula lutea?
Fovea centralis: a shallow depression with only cone cells at its center; ganglion cells and other conducting neurons are located only at its periphery. It lies directly opposite of the pupil and is where visual acuity or sharpness is maximal.
Macula lutea: This surrounds the fovea centralis. Here all layers of the retina are present and the two plexiform layers are rich in various carotenoids, which give the area a yellowish color. The carotenoids have antioxidant properties and filter potentially damaging short wavelength light, thus helping to protect the cone cells of the fovea.
What is the effect of light on the cGMP-gated sodium channel in the photoreceptor cell?
Light > absorbed by retinal of rhodopsin > isomerize from 11-cis-retinal to all-trans-retinal > activates opsin > activate transducin > stimulates phosphodiesterase to hydrolyze cGMP > cGMP-gated sodium channels close > hyperpolarization of cell > decrease release of neurotransmitters at synapse > depolarizes sets of bipolar neurons > action potentials sent to optic nerve > brain produces image.
Lens
Iris
34412
Ciliary body
34412
Vitreous body
Chorioid layer

30. Cellular structures through which light passes:
Cornea
Lens
Retina

31. Cornea cornea cornea Function: Protection Structural support
Filter out undesirable light rays
Focus image on retina
Nutrition:
Limbus
O2 from air for
corneal epithelium
cornea

32. Cornea

33. Cross section of human head

35. No blood vessels
in cornea

37. corneal layers Iris of Eye (toluidine blue)
292
Ciliary muscle:
smooth muscle
Sclera
Lens
Sclera-cornea junction (limbus)
Bowman's membrane
Aqueous
humor
Corneal stroma
Aqueous
humor
Corneal
endothelium
Iris
Descemet's
Membrane
Iris
Anterior
chamber
Posterior chamber

38. Stroma

39. Stroma

43. Limbus

44. Limbus

45. Lens
Function: Focus image on photosensitive portion of photoreceptor cells
Nutrition: Aqueous humor
Lens

49. Eye (toluidine blue) elongation of lens cuboidal cells at bow region
Lens cuboidal epithelium on its anterior surface gives rise to elongated lens fibers in the bow region, and the shared basement membrane of these cells is the capsule
Capsule
Lens cuboidal epithelium
292
Capsule
flattened lens fibers
No cuboidal
epithelium on the posterior surface of the lens and the capsule is thinner there
Artifactual space
34412

50. Lens

51. Cornea

52. Retina

53. Retina
Function: photoreception of image processing by neurons prevent backscatter of light
Nutrition: choroid, retinal blood vessels
retina

59. 34412 Cones Rods Ganglion cell layer Bipolar cells Vitreous body
Retinal
pigmented
epithelium
Artifactual space
Photosensitive
portion of rod
and cone cells
Retinal
pigmented
epithelium
Artifactual space
Venule in the
choroid plexus
Sclera

60. Retina (toluidine blue)
292
Ganglion cell layer
Bipolar cells
Artifactual space
Photoreceptor cells
Rods
Optic
nerve
Cones
Capillary

61. Cones have pigments for the primary colors (red, green, and blue)

62. Where do we find the primary colors (red, green, and blue)?

63. Light vs. dark adaptation

65. Function of retinal pigment Epithelium Vitamin A storage
Phagocytosis of rod tips
Absorption of light
Nutrients to retina
Blood retinal barrier

69. blind spot
macula

70. Blind spot

71. Eye monkey 34412 Capillary network in retina Pigmented layer
of epithelial cells
Elaborate network
of vessels, the
choroid plexus.
Central artery
of the retina

72. Macula
Blind spot

73. Blind spot

74. Macula

75. Typical retina
Macula

76. Structures which influence the image Iris Ciliary bodies Trabecular
meshwork

77. Iris Iris Function: regulate amount of light that reaches retina
blackened posterior surface to stop light rays
Dilator (myoepithelial)
and Constrictor (smooth) muscles
Nutrition: local blood vessels

78. Iris
Dilator (myoepithelial)
and Constrictor (smooth) muscle

79. Iris
Myoepithelial
Pigmented layer

80. Iris
Blue eye
Black eye

81. Pupil
Iris

83. 292 Eye (toluidine blue) Iris Anterior chamber Dilator muscle
Lens
Anterior chamber
Dilator
muscle
Lens capsule
Lens
Iris
Posterior chamber
Iris
pupil
Cuboidal
epithelium
on anterior
surface of
lens
Constrictor
muscle
Iris
Pupil

84. Lens and iris 192 and 34412 Iris Iris Lens anterior surface 192
Pigmented
epithelium of iris
Iris
Lens capsule
Posterior chamber
Iris
Lens cuboidal
epithelium
34412
Iris constrictor muscle is smooth muscle

85. Ciliary Bodies Function: Contraction of muscle
changes lens through zonules
Ciliary processes secrete aqueous humor
Blackened region stops light rays
Nutrition: local blood vessels

86. Ciliary Bodies
Contraction of muscle reduces tension on zonules allowing the lens to be more spherical to focus on close objects.

87. 292 Ciliary muscle: smooth muscle
Ciliary processes
Blood vessel
lens
Nerves
Ciliary muscle
192

88. Ciliary bodies
Lens
Lens capsule
Zonules

89. 34412 Eye monkey Sites of attachment of zonules to the lens’ capsule
Anterior surface
Eye monkey
Iris
Anterior surface
Posterior surface
Ligaments
(zonules)
lens
192
One site of attachment of a zonule to the capsule on the lens on its posterior surface
lens

90. 34412 Sclara Ciliary muscle Zonules 192 Lens fibers
Capsule and cuboidal epithelium on the anterior surface of lens
Thinner capsule on the posterior surface of the lens

91. Secretory epithelium and pigmented epithelium for the ciliary bodies

92. Pigmented layer contributes
to blood aqueous barrier

93. 192 192 Eye – secretory cells Pigmented cells of the ciliary processes
become the dilator
muscle of the iris
Pigmented cells
Secretory cells
Secretory cells
become the
pigmented cells
of the iris
Iris
Ciliary processes

94. Outflow of aqueous humor
IRIS

95. Trabecular Meshwork Function: resistance to outflow of aqueous humor
Nutrition: local blood vessels, probably aqueous humor
Trabecular Meshwork

96. Site of aqueous humor production
Outflow of aqueous humor
Site of aqueous humor production

97. Iris 34412 Canal of Schlemm Trabecular meshwork Blood vessels
Posterior chamber with
aqueous humor
Monkey eye
34412

98. Endothelium

100. Trabecular Meshwork Resistance to outflow of aqueous humor 229
Canal of Schlemm
Posterior chamber

101. In summary
The overall function of the EYE:

102. to observe the visual world